Re: [LARTC] Re: ADSL Calculator

[Andy Furniss <andy.furniss@dsl.pipex.com>]

Tobias Diedrich wrote:
> Per Marker Mortensen wrote:
> 
> 
>>http://www.adsl-optimizer.dk/thesis/
>>http://www.adsl-optimizer.dk/thesis/main_final.ps
>>
>>chapter 5, will give you extra information.
> 
> 
> Hmm, I still haven't read all of it, but I'd like to make two
> comments.
> 
> 1)
> I don't think the kernel patch is needed as you can fold that
> information into the rate table AFAICS (See the patch at the end
> of this mail).  Then again, depending on the overhead value you'd
> of course have a slight inaccuracy (in case the overhead is not
> divisible by 2^cell_log).  Thus in my patch I just assume the
> worst.

You end up either being a cell too safe around the optimal sizes even 
if, like you, your overhead is divisible by cell log. So you either have 
to undo your tweaking or underaccount for some packet sizes.

It's still better than doing nothing if you really can't change your 
kernel - Ed Wildgoose posted a similar patch some time ago.

> 
> 2)
> AFAICS you only looked at upstream shaping, right?
> At least from my experience I can say that for my ADSL link
> (3456kbit down / 448kbit up raw ATM speed, shared by 5 users)
> it is quite easy to saturate the downstream with a bittorrent
> download.  So some sort of downstream shaping is needed too.
> Unfortunately the IMQ patch seems to panic the kernel when it
> starts dropping packets.

If imq is unstable on your kernel you could try shaping download on 
egress / use a modified dummy device or use a policer on ingress.

Bittorrent is harder to shape than most things.

Andy.
_______________________________________________
LARTC mailing list
LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc